I wrote this little applet to test java version and link to
http://www.java.com if appropriate. It also has an image replacement should no java at all be installed.
I'd probably like it, for JGF.
At the moment, there's a webstart checker on there, which took ages to fix all Sun's shitty bugs where they haven't bothered to update their broken javascript.
Perhaps...collaborate to make something more "complete"? IIRC the webstart checker only properly works on MSIE - I'm sure it *could* work on opera + moz, but I've not found the code snippets to do that detection on those platforms, and I *don't know javascript and DOM*

.
Perhaps...a table with two boxes side-by-side; one is an applet-based check, the other a webstart-installed check.?